This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to 2000-052562 filed in Japan on Feb. 28, 2000; the entire content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a method for engraving characters, such as an identification number or name, into a surface of a workpiece made of a metal, and relates to an apparatus for achieving the method. More particularly, this invention relates to a method and an apparatus preferable for engraving on a workpiece having the same or the larger degree of hardness as that of a pen tip of the apparatus.
2. Description of Related Art
The prior art of an apparatus for engraving described above is disclosed, for example, in Japanese Examined Patent Application, Second Publication No. Hei 03-27398.
This apparatus is provided with a compression controller device which regulates an air pressure so that a pen tip of the apparatus can maintain a constant compression pressure applied to an engravement surface of a workpiece, in order to prevent a possibility of mis-engraving desired figures of characters, such as identification numbers or names, because of the variations in the compression pressure of the pen tip (stylus) for engraving between the shallow portions and the deep portions of an engraved region in case the region is large.
This apparatus can be used for a long time to engrave characters on a workpiece, if the workpiece has a lower hardness than that of the pen tip of the apparatus.
However, in case the apparatus of the prior art is applied to a workpiece having the same degree of hardness as that of the pen tip, a depth of indentation engraved by the apparatus on the workpiece is possible to a degree of only a few tens of micrometers in general, and the pen tip is capable of about thirty thousand strikes, corresponding to about 200 words engraved by the apparatus. That is, in case the apparatus is used for engraving a workpiece having the same degree of hardness as that of the pen tip, the pen tip is worn down in a short period with the result that the resistance of the apparatus becomes significantly lowered.
It is an object of the present invention to provide a method and an apparatus for engraving which can prevent a pen tip of the apparatus from being worn down in a short period so as to prolong the useful life of the apparatus, even if the apparatus is applied to a workpiece having the same or a greater degree of hardness as that of the pen tip.
In order to solve the problems described above, the present invention has provided the following methods and apparatuses.
A first aspect of the present invention provides a method which uses an apparatus comprising a pen, of which the tip is stricken against the workpiece for engraving characters, and a positioning unit for moving the pen tip to a position where the pen tip can engrave desired figures of characters into a portion of the workpiece to be engraved, wherein the portion of the workpiece is softened, preferably softened by irradiating a laser beam onto the portion, and then the pen tip is stricken against the workpiece in the softened state.
According to the first aspect described above, it is possible to reduce the wear and the damage of the pen tip which arise from friction between the workpiece and the pen tip by lowering the hardness of the portion to be engraved before applying the pen tip to the portion. Therefore, even if the hardness of the workpiece is the same or a larger degree than that of the pen tip, it is possible to prevent wear and damage of the pen tip in a short period of time, so as to prolong the useful life of the pen tip and to improve the durability and the reliablity of the apparatus.
A second aspect of the present invention provides an apparatus for engraving, which includes a pen, of which the tip is stricken to a portion of a workpiece to be engraved, a positioning unit for moving the pen tip on a surface of the workpiece, and an engravement portion softening device which lowers the hardness of the portion of a workpiece to be engraved.
In the second aspect, because this apparatus is equipped with the engravement portion softening device so as to soften the portion of the workpiece to be engraved, even if the workpiece has the same or a larger degree of hardness as the pen tip of the apparatus, it is possible to lower the hardness of the portion before the pen tip is stricken to the portion which is to be engraved. Thus, it is possible to reduce reliably the wear and the damage of the pen tip caused from friction between the pen tip and the workpiece, so as to prolong the useful life of the pen tip, and then to achieve the first aspect described above.
A third aspect of the present invention provides an apparatus for engraving, wherein the engravement portion softening device described above comprises either a first unit including a laser oscillator and a first optical system which condenses the laser beam irradiated from the laser oscillator onto the engravement portion of the workpiece, or a second unit including a laser oscillator and a second optical system which condenses the laser beam irradiated from the laser oscillator onto the engravement portion of the workpiece through an optical fiber.
In the third aspect, because the engravement portion softening device is equipped with either the first unit or the second unit described above, it is possible to soften reliably and easily the engravement portion of the workpiece by condensing the laser beam from the laser oscillator onto the engravement portion.
A forth aspect of the present invention provides an apparatus for engraving, wherein at least one of the laser oscillator, or the first or the second optical system described above is equipped to be moveable in an irradiation direction of the laser beam, and is provided a laser beam diameter controlling device which controls the diameter of the laser beam condensed onto the engravement portion of the workpiece.
In the fourth aspect, because the apparatus is constructed so as to be able to control the diameter of the laser beam condensed onto the engravement portion in accordance with the hardness and the thickness of the workpiece, even if the workpiece has the same or a larger degree of hardness as that of the pen tip of the apparatus, it is possible to reduce the wear and the damage of the pen tip arising from friction between the pen tip and the workpiece by decreasing the diameter of the laser beam. Thus, the pen tip of the apparatus enables prolonged use.
A fifth aspect of the present invention provides an apparatus for engraving, wherein the laser beam diameter controlling device includes a controller which automatically controls a position of the first or the second optical system described above.
In the fifth aspect, it is possible to control automatically the diameter of the laser beam condensed onto the engravement portion so as to soften the engravement portion with accuracy, by controlling the position of the first or the second optical system by means of the controller equipped with the apparatus.